MAMMALIAN SUBCLASSES. 273 



149, Z>, may extend over the cerebellum^ d, in Man not only do the 

 cerebral hemispheres, fig. 14 9, b, overlap the olfactory lobes and cere- 

 bellum, d, but they extend in advance of the one, and further back 

 than the other. Their posterior developement is so marked, that 

 anatomists have assigned to that part the character of a third 

 lobe ; it is peculiar, with its proportionally developed posterior 

 ventricular horn and ^ hippocampus minor,' to the genus Homo} 

 Concomitantly with the correspondingly developed anterior lobes 

 of the cerebrum, the ventricle is, in like manner, produced into a 



' Kuhl in Ateles Belzebuth,^ Tiedemann in the Macacque'' and Orang,<= Vrolik in 

 the Chimpanzee,*^ and myself in the Gorilla,® have severally shown all the homologous 

 parts of the human cerebral organ to exist, under modified forms and low grades of 

 developement, in Quadrumana. 



Kuhl rightly characterises the homologue of the posterior cornu, which he found 

 in a platyn-hine monkey, ' Anfang des hintern, dritten Horns dcs Seitenventri- 

 cels ' {op. cit. p. 70) — ' the beginning of the posterior or third horn of the lateral 

 ventricle.' Tiedemann, with equal accuracy, defines the answerable part in thecatar- 

 rhine quadrumana, as, ' Scrobiculus parvus loco cornu posterioris ' (pp. cit. p. 14). In 

 regard to the posterior cornu in the brain of the Orang he is silent as to any ' hippo- 

 campus minor.' It exists, however, in the condition described by Vrolik, in that Ape 

 and in the Chimpanzee, as ' une eminence que nous croyons avoir le droit de nommer 

 indice de pes hippocampi minor' ( Versl. en Mededeel. der Kon. Akad. 1862, p. xiii.) 

 These ' beginnings ' and ' indications' of structures which reach their full developement 

 in Man in no way afi^ect the value of the latter as zoological characters. In propound- 

 ing them as such to the Linna^an Society in 1857, I forbore to encumber my memoir 

 with reference to facts known to all who possessed the elements of Comparative Ana- 

 tomy. Tiedemann's definition was the accepted one : — ' Pedes hippocampi minores 

 vel ungues, vel calcaria avis, quce a postcriore corporis callosi tanquam processus duo 

 medullares proficiscuntur, inque fundo cornu posterioris plicas graciles et retroflexas 

 formant, in cerebro Simiarum desunt ; nee in ccrebro aliorum a me examinatorura 

 mammalium occurrunt ; Homini ergo proprii sunt.' (lb. p. 51.) In like manner 

 Cuvier had characterised the species of his order Quadrumana as having, ' Pouce 

 libre et opposable au lieu du grand orteil.' And he rightly affirms : ' L'homme est 

 le seul animal vraiment bimane et bipcde.' (Begne Animal, i. p. 70.) To adduce 

 beginnings of structures in one group which reach their full developement in another, 

 as invalidating their zoological application in such higher group, is puerile ; to repro- 

 duce the facts of such incipient and indicatory structures as new discoveries is ridicu- 

 lous ; to represent the statement of the zoological character of a higher group as a 

 denial of the existence of homologous parts in a lower one is disgraceful. Mr. Flower 

 was not the first to see in the hippocampal commissui-e the beginning of the corpus 

 callosum : the homologues of 'cornu posterius ' and of 'hippocampus minor' were 

 known in the Orang before Prof. Rolleston : and the homologies of the bones of the 

 hind foot in mammals had been determined before Prof. Huxley propounded them to 

 show that the hind thumb of the Ape was a great toe, and that Man was not the only- 

 animal who possessed two hands and two feet. 



" Beitrjige zur Zoologie und vergleichenden Anatomic, 4to, 1820, zweite Abthei- 

 lung, p. 70, tab. vii. ^ Icones cerebri Simiarum, fol. 1821, p. 14, fig. iii. 2. 



" Trevimnns, Zeitschrift fiir Pliysiologic, Bd. ii. s. 25, Taf. iv. '> Nieuwe Ver- 



handlungen der erste Klasse vom het Koningl. Nederhvndsche Institut. Amsterdam, 

 1849. « Fullcrian Lectures, Royal Institution (March 18, 1861), reported, with 



copies of diagrams, in 'Athenaeum,' March 23rd, 1861, p. 395. 

 VOL. II. T 



